1. Field of the Invention
The present invention relates to an image control unit for a video display unit (VDU) and more particularly to a video display unit in which control signals are provided in connection with blocks of characters covering a plurality of successive lines.
2. Prior Art
Image control units for video display units are generally known, and are commercially available in the form of integrated circuits. They provide the signals required for operation of display units, in particular cathode ray tubes having standardised BAS signal inputs. However when display units are used which do not conform to the standardised BAS signal inputs, then the video display units do not achieve their maximum exploitation of the image area at high frame frequencies. Moreover, when such image control units require cooperation with microprocessors, an additional expense is often required for extra components associated with the microprocessor. If a slow displacement of the data displayed on the display unit (sometimes referred to as a soft-scroll), is required, additional signals must be generated at predetermined times during construction of the image.
It is desirable to provide an apparatus which can produce the necessary control signals without complicated and expensive constructions.